There continues to be strong interest in the development of high temperature superconducting wires and tapes for applications such as magnets, transmission lines and magnetic energy storage systems. The superconducting material most usually employed for these tapes and wires is a 2-2-2-3 phase of lead-doped bismuth-strontium-calcium-copper oxide wherein the numbers represent the approximate respective molar ratios of the bismuth, strontium, calcium and copper substituents. In a typical wire preparation, a partially sintered powder, i.e., a powder consisting primarily of a combination of a 2-2-1-2 phase bismuth-strontium-calcium-copper oxide and other calcium, copper and lead-containing phases that will yield the desired 2-2-2-3 phase upon subsequent sintering, is loaded into a tube, e.g., a silver tube, and then mechanically deformed into a thin wire and/or tape. After deformation, the final conversion via sintering to the 2-2-2-3 phase takes place.
Various processes for the preparation of superconductors such as the lead-doped bismuth-strontium-calcium-copper oxide superconductor are known including preparation from the respective metal carbonates, metal oxides or metal nitrates. While such processes are known, these processes typically involve long sintering stages of about 2 weeks or longer. Thus, there remains a need for further simple, economical processes that will enable the preparation of the 2-2-2-3 lead-doped bismuth-strontium-calcium-copper oxide product.
In exploring the preparation of such lead-doped bismuth-strontium-calcium-copper oxide superconductors, the applicants have now discovered a precursor composition useful in the comparatively quick preparation of the 2-2-2-3 lead-doped bismuth-strontium-calcium-copper oxide product and a process of preparing the 2-2-2-3 lead-doped bismuth-strontium-calcium-copper oxide product from a solid state reaction of a mixture of Bi.sub.4 Sr.sub.3 Ca.sub.3 Cu.sub.4 O.sub.16.+-.z, alkaline earth cuprates and alkaline earth plumbates as solid solution precursors. Such a precursor composition for preparation of the 2-2-2-3 lead-doped bismuth-strontium-calcium-copper oxide product could be used in place of the partially sintered materials typically used at the present time in the preparation of superconducting wires and tapes.
Accordingly, it is an object of the present invention to provide a process of preparing a lead-doped BiSrCaCuO superconductor material.
Still another object of this invention is to provide a precursor composition that can be thermally processed to a lead-doped BiSrCaCuO superconductor material.